LMA

Every now and then, discussion amongst clinicians turns to the hypothetical of “what if you were stranded on a desert island?” and then leads into fierce debate on emergency drugs, preferred contents of a doctors bag or various airway devices.

Of course all of this is hypothetical – not many of us are going to be stranded, Lost-style, on a desert island and forced to manage an airway. In an ideal world we’d all work in a well-stocked theatre or ED with a variety of equipment to manage the difficult airway…

But many of us do work in areas where choice of equipment is needfully limited – such as in the prehospital and retrieval environment, or in rural & remote areas. Limitations may be imposed by cost, by size and shape, by weight or by need to fulfil various functions.

To my mind equipment for airway management in such areas should be not just readily available, but allow a suite of options, be affordable and offer advantages in both routine and emergency situations. Standard difficult airway plans usually revolve around Plans A, B, C & D

[of course, plans may be adapted to suit patient eg: initial plan for an awake fibreoptic, with back up plan in case of deterioration involving double-set up of ‘one look’ laryngoscopy, then rapid progression to a primary surgical airway in a case of massive supraglottic oedema, etc]

Much has been written elsewhere about DL vs VL and Emergency Surgical Airways. I won’t rehash them here, but instead point interested people towards EMcrit here and here respectively…. but what of the humble LMA in our airway plannng?

Available LMAs

For many years, the Classic LMA (cLMA) has been the stalwart of rescue ventilation. It is a familiar tool to many – indeed can be placed by trained volunteers such as ambulance officers in rural and remote areas. But the design has been improved; many second-generation LMAs offer the following :

integral bite-block

gastric drainage channel

ability to allow higher ventilation pressures

Many ambulance services have considered switching from the Classic LMA to the LMA Supreme (sLMA), as it has both bite-block, gastric drainage and allows higher pressures than the cLMA. However, like the cLMA, the sLMA is a lousy conduit for fibreoptic intubation.

Other devices exist, for example the Ambu AuraGain – an LMA which has bite block, gastric drainage and is specifically designed to function as a conduit for fibreoptic intubation via LMA. The iGel (pictured above) is in a similar mould, although like the Ambu does not allow BLIND passage of an ETT for intubation.

“the ability to place an ETT through an LMA, whether blind or with a fibreoptic scope, is a powerful combination for a back-up airway device”

Of course for placement of an ETT blindly through the LMA, there is the FastTrach intubating LMA. This has been around for a while, and allows blind intubation through the hyperangulated channel. Success rates for blind intubation through the device are good, reportedly at 81-100% – success can be improved to 95-100% with a flexible fibreoptic scope using the FastTrach as a conduit to facilitate intubation.

Flexible fibreoptic intubation is not a skill available in many austere environments, nor necessarily a skill of many emergency physicians…but a malleable fibreoptic stylet is both relatively easy to learn and can be a cheap addition to a difficult airway kit. But the hyperangulated channel of the Fastrach won’t accommodate a malleable stylet!

Other problems of the Fastrach are that it has no gastric drainage port, which seems to be a major downfall in a product designed as a rescue device in an emergency.

It is also notoriously difficult to remove the LMA over the ETT once in situ – best advice is to leave the LMA-ETT complex in situ once successfully placed, and perform a careful removal in a place of safety such as the operating theatre with multiple backups. There have been cases of the airway being lost during removal of the LMA over ETT, most notably as part of the cascade of catastrophes in the infamous Gordon Ewing’s or ‘exploding scrotum’ case…

Moreover the Fastrach is a bulky device and primarily used as a backup LMA specifically for placement of an ETT. It does not come in paediatric sizes. It would NOT be your primary LMA for rescue ventilation or use in a prehospital pack, although some use it as a backup backup LMA…

The Desert Island Airway

The IDEAL device for use as part of an airway kit in an austere environment (the ‘desert island airway’) should serve as a backup for laryngoscopy, allow gastric drainage, have an integral bite block, be relatively compact and able to serve as both primary and backup LMA, and finally to allow both BLIND and FIBREOPTIC intubation.

The AirQ is such a device. I think it’s the bees knees for my difficult airway kit – and I am not alone (EMcrit covered this device ages ago – it has seen some improvements since)

I had the unexpected good fortune to run into Dr Daniel Cook last week at Adelaide airport; Daniel was over in Adelaide for the ANZCA Anaesthetic Conference and headed stateside..whilst I was on y way to Melbourne to instruct on the rather excellent “critically ill airway” (CIA) course with a star-studded Australian faculty.

There are several AirQ devices in the family – I am a growing fan of the Air-Qsp blocker model. There’s no pilot balloon, the LMA cuff self-pressurises. Most importantly it comes in a variety of sizes and is both cheap and small enough to serve as primary rescue LMA AND as an intubating LMA.

If I had to chose one LMA only, then this device ticks boxes for both prehospital service or use on the airway trolley in an austere environment (ED resus, ICU, ward, rural etc). It has advantages of being

It’s also a lot less fiddly to remove an LMA over the ETT when placed via the AirQ than the Fastrach and has some nice touches – the anaesthetic circuit connector is detachable but is held in place via a plastic retainer (it’s very easy to drop these connectors when under stress or hands slick with saliva, blood or lube)…the packaging also contains a bronchoscope adaptor, allowing ongoing ventilation if decide to place an ETT by flexible fibreoptic scope – a little detail, but an absolute boon as prevents “needless faffing around looking for a bronch adaptor” in a time of crisis!

AirQsp Blocker – no pilot balloon, cuff self-pressurises. Anaes circuit connector held in place with a plastic retainer. Gastric tube channel allows passage of an orogastric drain. Packaged with lube and bronchoscope adaptor

Staged Airway Management for Transition from Prehospital to ED Care

But I think the REAL game-changer is that use of such a device allows a staged approach to airway management. In the past, I’ve seen ambulance services place a classic LMA for eg: OOHCA – typically this is where intubation is either not an option (volunteers or paramedics) or has failed despite being within their skill set (difficult intubation).

Leaving aside the fact that such the classic LMA device do not accommodate high ventilation pressures, their downfall is that that cannot function as a conduit for an ETT nor do they have a bite block or gastric drainage.

So the OOHCA survivor may arrive in ED Resus, with a soiled airway, biting down on the cLMA and now generating negative pressure pulmonary oedema….and the resus may grind to a halt as the ED team take out the LMA and perform laryngoscopy to place an ETT. We would see the same with the Supreme LMA (although both gastric drainage and bite block are significant advantages)…but due to the narrow diameter of the channel, the sLMA still needs to be removed if an ETT is to be placed. The iGel and Ambu AuraGain do allow passage of an ETT…but only with a flexible fibreoptic scope – rarely available immediately in ED. So blind intubation is probably best in the ED via an LMA placed earlier in the prehospital arena…

The Fastrach allows blind intubation, but is expensive and bulky, so unlikely to be used as the primary back up airway in a prehospital service. Gastric drainage is not possible unless one deflates the cuff to allow tube passage…it’s a good device…but too expensive and bulky to be used as primary LMA, in my opinion.

To my mind the Air-Q LMA actually allows a staged approach to airway and progression from prehospital to hospital or as ascend the airway skill gradient. Specifically, it is

small enough and cheap enough to be available across a prehospital service or rural hospital network

allow gastric drainage and high ventilation pressures, with an integral bite block

can be placed by relatively inexperienced staff

then allows an ETT can be placed blindly by success rate improved with either a malleable fibreoptic stylet or a flexible fibreoptic scope in the ED whilst resus continues…

I’ve never worked in an ED where flexible fibreoptic is immediately available (perhaps it should!)…but the reality is that flexible fibreoptic is a skill that needs regular skills maintenance – whereas the use of a malleable fibreoptic stylet (such as the Levitan FPS) is pretty straightforward and can be easily used through the AirQ…

So – if I could only have one LMA, I’d go for the Air-Q. Admittedly the blind intubation rate isn’t as good as Fastrach (although this can be improved by extension of the neck and application external laryngeal manipulation) – but it is small, affordable, comes in a range of sizes and allows a staged progression in airway management without interruption – indeed it appears designed for this.

On this basis, it is my recommendation for a single LMA with variety of uses in prehospital and rural environments where flexible fibreoptic scopes are not available.

The table below summarises pros and cons of various LMAs discussed above.

I should add that the AirQ comes in paediatric sizes – unlike the Fastrach…

Tim Leeuwenburg

RESUSCITATE - DIFFERENTIATE - INVESTIGATE

I am a Rural Doctor on Kangaroo Island, South Australia with interests in emergency medicine, anaesthetics & trauma. When not working I enjoy fiddling with chainsaws and seakayaking. Along with partner Patricia we rehabilitate orphaned wildlife and devise roadkill recipes.